1. Field of the Invention
The present invention relates to an improvement of an axial flow fan motor to be used for such purposes as heat radiation of office automation (OA) equipment and the like.
2. Description of Related Art
In OA equipment, such as personal computers and copy machines, many electronic components are housed within the casing thereof. Accordingly, the temperature in the casing rises due to the heat generated by these electronic components such that the electronic components way be damaged or their characteristics degraded by the heat. Recently there has been a rising demand to make equipment smaller so that electronic components are housed tightly packed within the casing, which markedly increases the possibility of this type of damage by heat.
In regard to this, damage by heat can be prevented by providing an air flow hole in the casing of the equipment and installing an axial flow fan motor there so that the heat within the casing can be forcibly discharged outside.
However, the method of forcibly discharging heat using a motor leads to a critical problem in that almost all of the heat discharging functionality is lost if the motor fails. The main conventional method to avoid this problem is to arrange two axial flow fan motors stacked in the axial direction in the air flow hole of the casing.
This is normally done to maintain the heat discharging functionality by driving one of the two axial flow fan motors, and driving the other if the first fails.
In this case, however, of the two axial flow fan motors, the blades of the fan motor which is stopped obstruct the airflow from the fan motor which is being driven. Because of this, a fan motor with fewer blades has been used. This type of conventional axial flow fan motor is shown in FIG. 6.
As shown in the figure, this type of axial flow fan motor has a casing 1 in which a ventilation hole 1a is formed in the center portion thereof, an outer rotor motor 2 fixed in the center of the ventilation hole 1a, and blades 3 attached to the outer periphery of this motor 2.
In this case, a plurality of blades 3, three here, are mounted to the outer periphery of the motor 2 by being formed on the outer periphery of a ring 4, as shown in FIG. 7, and this ring 4 then being fitted and fixed around the outer periphery of the motor 2 (rotor outer periphery) shown in FIG. 6.
Accordingly, the blades 3 rotate along with the driving of the motor 2 (rotor rotation) This forces air flow in the axial direction of the motor, thus discharging heat from within the casing of the equipment.
Referring to FIG. 6, reference numeral 1b denotes a mounting hole for mounting the axial flow fan motor to the equipment casing and the like (not shown); reference numeral 5 denotes a spoke used for supporting the motor 2; and reference numeral 6 denotes an electric power supply wire.
The conventional axial flow fan motor is provided with fewer blades 3 than usual, as is evident from FIG. 7, and there is a large opening between adjacent blades 3 and 3.
As a result, a large opening 7 through which air can flow linearly in the axial direction is formed between the blades 5 and 3. Therefore, when two of this type of fan motor are stacked in the axial direction, as shown in FIG. 8, the degree to which the blades 3 of the fan motor that is stopped, for example, a fan motor 61b (see FIG. 6), obstruct the air flow (see arrow xcex1) from the fan motor that is being driven, for example, the fan motor 61a, is decreased. Also, airflow in the axial direction of the motor when the motor is stopped is improved even if only one fan motor is being used.
On the other hand, however, this leads to a problem of decreased airflow, for which there has been demand for improvement.
In view of the foregoing demand, it is an object of the present invention to provide an axial flow fan motor capable of improving airflow in the axial direction of the motor when the motor is stopped, while minimizing a decrease of airflow.
In order to achieve this object, according to a first aspect of the present invention, an axial flow fan motor comprises a casing having a ventilation hole formed in the center portion thereof, a motor fixed in the center of the ventilation hole, and a plurality of blades which rotate around a motor rotation axis along with rotation of the motor, which has openings enabling air flow linearly in the axial direction between the blades, wherein the plurality of blades are arranged at different intervals circumferentially around the rotation axis of the motor.
According to a second aspect of the present invention, an axial flow fan motor comprises a casing having a ventilation hole formed in the center portion thereof, a motor fired in the center of the ventilation hole, and a plurality of blades which rotate around a motor rotation axis along with rotation of the motor, which has openings enabling air flow linearly in the axial direction between the blades, wherein the plurality of blades are arranged at equal intervals every other blade circumferentially around the rotation axis of the motor.
According to the present invention as described above, in an axial flow fan motor having openings through which air can flow linearly in the axial direction provided between a plurality of blades which rotate around the rotation axis of the motor along with the rotation of the motor, the plurality of blades are arranged at different intervals or at equal intervals every other blade circumferentialy around the rotation axis of the motor. As a result, a decrease in airflow can be minimized while airflow in the axial direction of the motor when the motor is stopped can be increased.
Therefore, in an application in which one or more fan motors, of a plurality of axial flow fan motors of the present invention as described above which are stacked in the axial direction, is optionally selected to be used, the degree to which the blades of the fan motor(s) that is slopped obstruct the air flow from the fan motor(s) that is being driven is decreased. Moreover, a decrease in airflow can meanwhile be minimized.